Cobalt deficiency effects on trace elements, hormones and enzymes involvedin energy metabolism of cattle

This study was conducted to investigate the physiological consequences of l ong-term moderate cobalt deficiency in beef cattle, which have not hitherto been studied in detail. Cobalt deficiency was induced in cattle by feeding two groups of animals either a basal corn silage-based diet that was moder ately low in cobalt (83 mu g Co/kg), or the same diet supplemented with cob alt to a total of 100 mu g per kg, for 33 weeks. Cobalt deficiency was indu ced, as judged by inappetance, diminished growth gain and a markedly reduce d vitamin B-12 status in serum and liver. The long-term cobalt deprivation which was primarily a combination of reduced feed intake and a tissue vitam in B-12 deficiency did not show evidence of a significant dysfunktion of en ergy metabolism, The activities of glucose-6-phosphate dehydrogenase and cy tochrome oxidase in liver remained unaffected by cobalt deficiency, nor was there a significant change in serum glucose level of cattle on the cobalt- deprived diet. However, analysis of thyroid hormone status indicated a slig ht reduction of type I thyroxine monodeiodinase activity in liver accompani ed by a significant reduction of the triiodothyronine level in serum. The d iminished liver vitamin B-12 level resulted in significantly reduced folate level in this tissue, reduced concentrations bf heme-depending blood param eters. Moreover cobalt deficiency or rather vitamin B-12 deficiency was acc ompanied by a dramatic accumulation of the trace elements iron and nickel i n liver. These results: indicate that long-term moderate cobalt deficiency may induce a number of physiological changes in cattle, but a follow-up stu dy, which excluded different feed levels by including a pair-fed control gr oup, will be neccessary to actually obtain the single effect of cobalt defi ciency in cattle.